Count unique values for every column

Question

I would like to return the count of the unique values for every column in a table. For example, if I have the table:

 Testdata <- data.frame(var_1 = c(\"a         


        

Answer 1

You could use apply:

apply(Testdata, 2, function(x) length(unique(x)))
# var_1 var_2 var_3 
#     1     1     3